Technical Field
The present invention relates to an image-forming apparatus that forms an image on a long sheet.
Background Art
In the past, an electro photographic image-forming apparatus such as a printer, a copier and the like has been known. In such an image-forming apparatus, an image has been formed with sheets contained in a feeding tray being conveyed one by one.
A size of the sheet containable in a feeding tray installed inside the image-forming apparatus, particularly, a length of the sheet along a conveying direction of the sheet is fixed by a size of the image-forming apparatus. On the other hand, in a feeding tray, called as “manual feed tray”, which is installed outside the image-forming apparatus, any long sheet can be put thereon regardless of the size of the image-forming apparatus. Accordingly, an image-forming apparatus by which a long sheet being longer than a length of the feeding tray along the conveying direction thereof may be put on the feeding tray and an image can be formed on the long sheet has been proposed.
Here, in a sheet-feeding operation from the manual feed tray, a technology of changing any conveying speeds of the sheet in order to increase a number of the conveying sheets per unit time has also been proposed (see Japanese Patent Application Publication No. H05-246094).
FIGS. 1A through 1C show conditions in each of which a sheet is put on the external feeding tray. FIG. 2 shows a condition in which the sheet is put on the external feeding tray and is conveyed from the external feeding tray. When a length L of a sheet P is shorter than a length L10 of an external feeding tray 20, a rear end of the sheet P does not hang down from a rear end position P1 of the external feeding tray 20, as shown in FIG. 1A. In this condition, it is possible to securely convey the sheet.
When a sheet P has high stiffness even in a case where a length L of a sheet P is longer than a length L10 of an external feeding tray 20, a rear end of the sheet P does not hang down from a rear end position P1 of the external feeding tray 20, as shown in FIG. 1B. In this condition, it is also possible to securely convey the sheet.
On the other hand, when a sheet P has low stiffness and a length L of a sheet P is longer than a length L10 of an external feeding tray 20, a rear end of the sheet P hangs down from a rear end position P1 of the external feeding tray 20, as shown in FIG. 1C. When the rear end of the sheet P hangs down from the rear end position P1 of the external feeding tray 20, any resistance force shown by an arrow R in FIG. 2 is applied to a part B1 of the sheet P put on the external feeding tray 20 against any conveying force F shown by an arrow F in FIG. 2. Thus, the part B1 of the sheet P is pulled in parallel with the conveying direction of the sheet P.
In, however, a part B2 of the sheet P hanged down from the rear end position P1 of the external feeding tray 20, the conveying force F is not applied in parallel with the conveying direction of the sheet P so that the sheet P may be caught by the rear end position P1 of the external feeding tray 20. When the sheet P may be caught by the rear end position P1 of the external feeding tray 20, the rear end of the sheet P may raise as shown by the dotted line in FIG. 2 by any counterforce.
This raise of the rear end of the sheet P may cause the part B1 of the sheet P put on the external feeding tray 20 to raise from the external feeding tray 20. On the external feeding tray 20, guide plates 200 are provided along a width direction of the sheet P to correct any deflection of the sheet P. When the part 31 of the sheet P put on the external feeding tray 20 raises from the external feeding tray 20 as shown by a long dashed short dashed line in FIG. 2, the sheet P may contact the guide plates 200 correctly so that the sheet P may be deflected. Such a deflection may cause any poor functioning such as defective image, crumpled sheet and the like to occur. This may deteriorate any printing quality. In the past, any image-forming apparatus to address such poor functioning which may occur when feeding the long sheet has not been proposed.